muscle tissue

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Questions and Answers

Which property of muscle tissue describes its ability to respond to nerve signals?

Extensibility

Excitability (correct)

Elasticity

Contractility

What is the primary function of skeletal muscle tissue?

Controlling involuntary movements

Generating thermal energy

Connecting to blood vessels

Maintaining posture (correct)

Which type of muscle tissue is characterized as striated and under voluntary control?

Cardiac muscle

Connective tissue

Smooth muscle

Skeletal muscle (correct)

Which characteristic of skeletal muscle is indicated by having multiple nuclei within its fibers?

Multi-nucleation Signup and view all the answers

What is the role of muscle tissue in thermogenesis?

Generating heat through contraction Signup and view all the answers

Which type of muscle fiber organization is characterized by a branched tendon with muscle fibers arranged around each branch?

Multipennate Signup and view all the answers

Which of the following describes a muscle that reduces the diameter of openings in the body?

Circular Signup and view all the answers

Which classification refers to muscles named based on their location in the body?

Relative position Signup and view all the answers

In a biceps curl, which muscles act as synergists to help stabilize the joint and assist in movement?

Brachioradialis and Brachialis Signup and view all the answers

What is the role of fixator muscles during movement?

To stabilize proximal joints Signup and view all the answers

Which muscle classification is based on the number of heads of origin?

Biceps brachii Signup and view all the answers

What is the main action performed by agonist muscles during movement?

Bring about the desired movement Signup and view all the answers

Which attribute characterizes the muscle named 'gluteus maximus'?

Size Signup and view all the answers

Which term refers to a muscle that opposes the action of agonists?

Antagonist Signup and view all the answers

What characteristic is associated with nuclei in skeletal muscle fibers?

Multinucleated and peripheral distribution Signup and view all the answers

Which connective tissue component surrounds individual muscle fibers?

Endomysium Signup and view all the answers

What type of muscle attachment typically remains fixed during contraction?

Origin attachment Signup and view all the answers

Which of the following correctly describes the speed of contraction in skeletal muscle?

Fast Signup and view all the answers

What is the primary neurotransmitter that regulates contractions in skeletal muscle?

Acetylcholine Signup and view all the answers

Which muscle organization type has fibers that run parallel to the length of the muscle?

Parallel muscles Signup and view all the answers

Which connective tissue component helps to support muscles and connects them to bones?

Aponeurosis Signup and view all the answers

What is the role of the rotator cuff in relation to movement?

It fixes the shoulder during the biceps curl. Signup and view all the answers

Which connective tissue sheath surrounds the entire muscle?

Epimysium Signup and view all the answers

What is the function of the T-tubules in muscle cells?

They permit rapid transmission of action potential into the cell. Signup and view all the answers

How are myofibrils organized within muscle fibers?

They are connected by the sarcomeres. Signup and view all the answers

What distinguishes the A Band from the I Band in myofibrils?

A Band contains both thick and thin myofilaments. Signup and view all the answers

What type of muscles are characterized as involuntary and non-striated?

Smooth muscle Signup and view all the answers

What component surrounds each individual muscle fiber?

Endomysium Signup and view all the answers

Which structure is primarily responsible for storing calcium in muscle cells?

Sarcoplasmic reticulum Signup and view all the answers

What distinguishes thick myofilaments from thin myofilaments?

Thick myofilaments primarily consist of myosin. Signup and view all the answers

Study Notes

Muscle Tissue Overview

Muscle tissue is specialized for contraction, producing voluntary or involuntary body part movement.
It is one of the basic tissues in the body.
Muscle cells (fibers/myocytes) are elongated and narrow.
"Sarco" is Greek for muscle; "Myo" is Latin for muscle. These prefixes are used in describing muscle.

Properties of Muscle Tissue

Excitability: Responds to nerve signals by generating electrical signals.
Contractility: Shortens and generates force.
Extensibility: Can be stretched.
Elasticity: Returns to its original shape.

Functions of Muscle Tissue

Movement.
Maintaining posture.
Stabilizing joints.
Thermogenesis (transforming chemical energy to mechanical energy, thus creating force).
Increasing muscle mass, boosting the immune system.

Types of Muscle Tissue

Skeletal muscle
Smooth muscle
Cardiac muscle

Skeletal Muscle

Connects to bones via tendons, enabling a wide range of movements and functions.
It is the most common and abundant muscle type.
It is striated and under voluntary control.
Examples include muscles in the limbs and body wall.

Characteristics of Skeletal Muscle

Microscopic: Long cylindrical fibers (muscle cells/myocytes), cross-striations, multiple nuclei (peripherally distributed), and unbranched.
Location: Attached to bones via tendons.
Nervous Control: Voluntary, supplied by somatic nerves, governed by the somatic nervous system.
Speed of Contraction: Fast.
Size: Very large (10-100 µm diameter, up to 35 cm length).
Connective Tissue Components: Endomysium, perimysium, epimysium.
Contractile Proteins: Organized into sarcomeres.
Junctions/Rhythmicity: No junctions between muscle fibers, no auto-rhythmicity.
Regulator Proteins: Troponin and Tropomyosin; regulate contraction.

Parts of a Muscle

Belly: The fleshy part of the muscle.
Tendons: Fibrous parts, tightly connected to the bones or cartilage. More collagen fibers, less vascular, non-elastic.
Aponeurosis: Thin fibrous connective tissue sheets that connect muscles to bones and provide stability and strength, especially in flat muscles like abdominal aponeurosis.

Attachments of Muscles

Origin: Relatively fixed attachment point during muscle contraction; generally located proximally (closer to the center of the body).
Insertion: Attachment that moves during muscle contraction; generally located distally (further from the center of the body).

Muscle Organization (Arrangement of Muscle Fibers)

Parallel Muscles: Muscle fibers run parallel to the muscle's length. This is the most common type in the skeletal muscles. Examples of different parallel muscles include: fusiform, strap, and quadrilateral muscles, including the biceps brachii, sartorius, and pronator quadratus.
Convergent Muscles: Muscle fibers spread out like a fan at one end and converge to a single point at the other, like the pectoralis major.
Pennate Muscles: Muscle fibers are arranged at an angle to the tendon like a feather. Include different types: unipennate (e.g., palmar interossei), bipennate (e.g., dorsal interossei) and multipennate (e.g., deltoid).
Circular Muscles: Muscle fibers arranged concentrically around an opening, such as the orbicularis oculi and orbicularis oris.

Nomenclature of Muscles

Shape, Size, Origin, Number of Heads, Location.

Actions of Skeletal Muscles

Agonist (Prime Mover): Muscle primarily responsible for a specific movement; directly brings about the intended movement.
Antagonist: Muscle opposing the action of the agonist.
Synergist: Muscle assisting the agonist to perform its action, stabilizing the joint during the movement.
Fixator: Stabilizes proximal joints to allow distal joint movement; a body part stabilizer during a movement of another part; example includes rotator cuff muscles during biceps curl.

Skeletal Muscle Structure

Surrounded by epimysium (connective tissue).
Composed of bundles of muscle fibers called fascicles, encased by perimysium.
Individual muscle fibers have endomysium, a connective tissue sheath.

Skeletal Muscle Fiber Structure

Contains myofibrils, bundles of contractile proteins.
Myofibrils are composed of numerous sarcomeres, functional units of contraction.
Sarcomeres are divided by Z lines.
Myofilaments: Actin (thin) and Myosin (thick), making up sarcomeres.
Striations: The overlap pattern of thick and thin filaments creates the striped appearance of skeletal muscles.
T tubules: Membrane invaginations.
Sarcolemma: Plasma membrane of the muscle fiber.
Sarcoplasmic reticulum: Smooth endoplasmic reticulum that stores calcium.

Smooth Muscle

Involuntary, non-striated muscle, fusiform shape, single, centrally located nucleus.
Located in the skin (arrector pili muscles), reproductive/respiratory/urinary tracts, hollow organs (e.g., intestines, bladder, uterus, stomach), vessels (blood vessels), and eyes (iris contraction/dilation and lens movement).

Characteristics of Smooth Muscle

Elongated, spindle-shaped cells.
Centrally located nucleus.
Absence of striations, myofibrils, sarcomeres, and T tubules.
Supplied by autonomic nerves, involuntary.
Small size (3-8 µm diameter).
Only endomysium connective tissue component.
Gap junctions in visceral smooth muscle.
Auto-rhythmicity of visceral smooth muscle.
Slow speed of contraction.

Smooth Muscle Structure

Filaments (thick myosin, thin actin).
Dense bodies (similar to Z disks in striated muscle), which link filaments and transmits the contractile forces.

Cardiac Muscle

Involuntary, striated muscle.
Exclusively in the heart (myocardium).
Muscle fibers branch and interconnect, forming a network.
Muscle fibers are short, branched, cylindrical.
Cells (cardiomyocytes) connected by intercalated disks (allow communication and rapid signal transmission)
Contains large mitochondria.
Contains prominent transverse striations.
Moderate speed of contraction.
Contains troponin and tropomyosin regulator proteins.

Diseases of the Muscle Tissue

Myasthenia Gravis: Neuromuscular disorder; weakness in skeletal muscles, caused by communication impairment between nerve cells and muscles. Autoimmune; antibodies attack components of the postsynaptic membrane, impairing neuromuscular transmission.
Duchenne Muscular Dystrophy: Progressive weakening and loss of skeletal and heart muscle, genetic disorder arising from a mutation in the dystrophin gene.

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